Definition
Air changes per hour is the volumetric airflow divided by the room volume, expressed per hour:
ACH = (volumetric_flow_rate / room_volume) x 3600
An ACH of 6 means the room air is theoretically replaced six times in an hour.
Typical values
- Classrooms: about 4-6 ACH (see school ventilation)
- Laboratories and fume hoods: 6-12 ACH (lab recovery)
- Operating theatres: 20+ ACH (hospital recovery)
- Offices: 2-4 ACH
Why ACH matters for recovery
Higher ACH means more outdoor air to condition and more exhaust energy to reclaim. Spaces with high ACH and high hours of operation are exactly where an Cœur de récupération intégré à l'AHU pays back fastest, because the recovered energy scales with the airflow.
Frequently asked questions
Does high ACH mean better air quality? Up to a point; beyond code minimums, filtration and distribution often matter more than raw rate.
Is ACH the same as outdoor-air rate? Not always – ACH can include recirculated air; the recovery benefit tracks the outdoor fraction specifically.
Need help specifying the right air-to-air heat recovery for your project? Contact the QIYU engineering team – WhatsApp +86 157 5335 5505, or email kuns913@gmail.com.
Questions fréquemment posées
What is ACH in ventilation?
Air changes per hour is the volumetric outdoor-air supply divided by the room volume, i.e. how many times the room air is replaced each hour.
Why does higher ACH increase recovery value?
More outdoor air means more conditioning load to recover; at high ACH the energy carried by the exhaust is large, so even modest effectiveness saves substantial heating or cooling energy.
Questions fréquemment posées
What is ACH in ventilation?
Air changes per hour is the volumetric outdoor-air supply divided by the room volume, i.e. how many times the room air is replaced each hour.
Why does higher ACH increase recovery value?
More outdoor air means more conditioning load to recover; at high ACH the energy carried by the exhaust is large, so even modest effectiveness saves substantial heating or cooling energy.
Spécifiez le bon échangeur
Nos ingénieurs dimensionnent le noyau selon votre débit, température et budget de perte de charge, et choisissent la récupération par plaque, rotative ou caloduc selon l'application. Lisez le guide de l'échangeur , ou contactez-nous pour une spécification.
Produits connexes
Récupération par plaque, rotative ou caloduc pour le CVC et la ventilation.
Noyaux stationnaires à grande surface pour l'air et le liquide.
Récupération d'énergie à haute efficacité pour grands débits.
Courants passifs et totalement séparés pour applications propres.